|Ph.D Student||Maayani Shai|
|Department||Department of Mechanical Engineering||Supervisor||Professor Tal Carmon|
|Full Thesis text|
Everyone is familiar with water waves, scientifically known as capillary waves. In my research, I design, fabricate, and experimentally demonstrated, for the first time, a hybrid optocapillary device that allows energy exchanging between light and capillary waves as well as stimulated amplification in the form of a water wave laser. Capillary waves are unique to the liquid phase of matter, important in surface science, and relates to interfacial tension originating from the attraction between intimate fluid particles. Therefore, they might be considered as the most important wave in microfluidics. Despite that, optofluidic devices where light exchanges energy with capillary waves were not previously considered, not even theoretically suggested. This is because the quantum efficiency of energy exchanging between light and capillary waves is proportional to the ratio between the frequency of capillary waves and the optical frequency. As capillary waves are at the kHz-rate range, their quantum efficiency is low.
Here we mitigate this low quantum efficiency by fabricating a new type of optical droplet resonators, where evaporation is compensated for via a nanofluidic contact with an infinitely large reservoir, allowing an optical quality factor (Q) of 300,000,000 and a finesse of a 1,000,000. Our finesse is second to none in optofluidics devices and equals to the finesse in microcavities made of solids.
This said, scientific research is more than just a “Q race” toward a better enhancement of light. The essence of research is in leveraging the parameters of our system, including its Q, to be high enough for observing new phenomena. In this respect, we increase Q to a degree that was sufficient for sideband cooling of capillary waves, that was shown for the first time in any system in nature. Going to the other sideband of the resonance allow water-wave laser that is also shown here for the first time in any system in nature.
Our opto-capillary cavity is a million times softer than what the current solid-based technology can provide. Such softness accordingly enhances optically-induced deformation, which can benefit optical cooling of capillary waves. Such a dramatic improvement in cooling might take capillary waves, in the future, toward their quantum ground state, while the system is maintained at room temperature and pressure.
In what mentioned above, I was using light to induce or cool mechanical vibration at liquid-phase boundaries, in the last part of my research I am using a mechanical rotation of a resonator to build a new type of device - a rotating-resonator isolator with record 99.6% fidelity. My work is therefore using mechanics to extend the boundaries of optics; and vice versa, using optics to extend the boundaries of mechanics.